High-spatial resolution Chandra x-ray obsrvations have
demonstrated that most of Jupiter's northern auroral x-rays
come from a hot spot located significantly poleward of the
latitudes connected to the inner magnetosphere. This hot
spot appears fixed in magnetic latitude and longitude and
coincides with a region exhibiting anomalous ultraviolet and
infrared emissions. The hot spot also exhibited
approximately 45 minute quasi-periodic oscillations, a
period similar to those reported for high-latitude radio and
energetic electron bursts observed by near-Jupiter
spacecraft. These results invalidate the idea that jovian
auroral x-ray emissions are mainly excited by steady
precipitation of energetic heavy ions from the inner
magnetosphere. Instead, the x-rays appear to result from
currently unexplained processes in the outer magnetosphere
that produce highly localized and highly variable emissions
over an extremely wide range of wavelengths. The Chandra
observations also revealed for the first time x-ray emission
(about 0.1 GW) from the Io Plasma Torus, as well as very
faint x-ray emission (about 1-2 MW) from the Galilean moons
Io, Europa, and possibly Ganymede. The emission from the
moons is almost certainly due to Kalpha emission of surface
atoms (and possibly impact atoms) excited by the impact of
highly energetic protons, oxygen, and sulfur atoms and ions
from the Torus. The Torus emission is less well understood
at present, although bremsstrahlung from the non-thermal
tail of the electron distribution may provide a significant
fraction. In any case, further observations, already
accepted and in the process of being planned, with Chandra,
some with the moderate energy resolution of the CCD camera,
together with simultaneous Hubble Space Telescope
observations and hopefully ground-based IRTF observations
should soon provide greater insight into these various
processes.

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